1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device which can reduce a brightness difference between pixels to improve the quality of an image.
2. Discussion of the Related Art
In general, a liquid crystal display (LCD) device is adapted to display an image by adjusting light transmittance of liquid crystal cells depending on a video signal. An LCD device of an active matrix type is advantageous in displaying moving images in that a switching element is formed for every liquid crystal cell therein. A thin film transistor (TFT) is mainly used as the switching element.
In order to reduce the number of data lines in an LCD device, recently, much attention has been paid to a Data Line Sharing (DLS) technology in which adjacent pixels displaying different colors share one data line with each other.
Where the data line is driven in a two-dot driving manner, it is alternately charged with a positive data signal and a negative data signal during an interval of two horizontal period (2H). In this case, the data line may be successively charged with the same polarity over two adjacent periods or be charged from a positive polarity to a negative polarity (or from the negative polarity to the positive polarity) over the two adjacent periods. That is, the charged state of the data line may undergo a change.
For this reason, pixels displaying the same color may exhibit a brightness difference therebetween based on the charged states of the corresponding data lines even though they are supplied with data signals of the same gray scale. In particular, such a brightness difference between green pixels expressing a green color is very visible.
FIG. 1 is a graph showing visibilities based on wavelengths of light. It can be seen from this drawing that a green light exhibits higher visibility than a red light and a blue light. The higher visibility means that even a small brightness variation is easily seen by the human eye. In other words, because the green light exhibits higher visibility than the lights of the other colors, even a small brightness variation thereof is easily seen by the human eye. As a result, the brightness of one unit pixel consisting of a red pixel cell, a green pixel cell and a blue pixel cell can be considered to depend on the brightness of the green pixel cell. Consequently, in order to improve the picture quality of the LCD device, it is important to reduce a brightness difference between green pixels emitting the green light.